1. Field of the Inventions
The present inventions relate to cooling systems, and more particularly, to cooling systems for outboard motors.
2. Description of the Related Art
Outboard motors typically include an exhaust passage for discharging exhaust gases from an engine to an external location. Additionally, outboard motors usually include a cooling water passage configured to introduce cooling water from the body of water in which the outboard motor is operating, to cool the engine.
In addition, another cooling water passage is usually defined in an upper portion of a casing that forms an outer wall of the outboard motor. For example, outboard motors usually include a cooling jacket that extends along respective inner side surfaces of an upper casing which houses a driveshaft that extends from the engine, and a lower casing, which has a propulsion shaft coupled with the driveshaft through a power transmission mechanism, to prevent the upper portion of the casing from being heated by the exhaust gases that have a high temperature and passing through the exhaust passage. A lower portion of the casing is usually placed below a surface of the water body when the associated watercraft runs. The outside water, such as seawater, thus can enter a lower portion of the exhaust passage. Accordingly, the lower portion of the casing can be cooled by seawater or the like.
However, a portion of each inner side surface of the casing positioned slightly above the water surface can be heated by the exhaust gases passing through the exhaust passage. As a result, a portion of each outer side surface of the casing corresponding to the inner portion heated by the exhaust gases can have a high temperature. Under these circumstances, if the seawater adheres to the portions of the outer side surfaces, a calcium component of the seawater can be separated to whiten the outer side surfaces of the casing. Japanese Patent Publication Number JP-A Hei08-034393 discloses a cooling mechanism at a portion of the casing that can be positioned above the water surface.
This outboard motor has water guiding passages allowing a portion of the cooling water that has already cooled the engine to fall along respective portions of the outer side surfaces of the casing that are exposed above the water line when the watercraft is moving. Because the portion of the cooling water is discharged to the respective portions of the outer side surfaces from the water guiding passages, the whitening of the outer surfaces can be reduced.